(1) Field of the Invention
The present invention relates to a thrust bearing which receives an axial force of a crankshaft of an internal combustion engine.
(2) Description of Related Art
A crankshaft of an internal combustion engine is rotatably supported, at its journal portion, in a lower part of a cylinder block of the internal combustion engine via a main bearing which is configured by combining a pair of half bearings into a cylindrical shape.
One or both of the pair of half bearings is used in combination with a half thrust bearing which receives an axial force of the crankshaft. The half thrust bearing is provided at one or both of axial end surfaces of the half bearing.
The half thrust bearing receives an axial force generated in the crankshaft. That is, the half thrust bearing is provided for the purpose of bearing the axial force inputted to the crankshaft when the crankshaft is connected to a transmission via a clutch, for example.
On a sliding surface side of the half thrust bearing near both circumferential ends thereof, thrust reliefs are formed so that a bearing member becomes thinner toward the respective circumferential end surfaces. In general, the thrust relief is formed so that a length from the circumferential end surface to the sliding surface of the half thrust bearing, and a depth at the circumferential end surface are constant irrespective of the position in a radial direction. The thrust relief is formed in order to absorb misalignment of the end surfaces of a pair of half thrust bearings when the half thrust bearings are mounted on a split type bearing housing (see FIG. 10 of JP H11-201145 A).
Further, conventionally, there is also proposed a technique in which, in consideration of the deflection deformation of a crankshaft during operation of an internal combustion engine, a crowning surface having a curved surface shape is provided on at least an outer diameter side of a sliding surface of the half thrust bearing, thereby reducing the local contact stress between the sliding surface of the half thrust bearing and the crankshaft (JP 2013-019517 A).
In addition, there is also proposed a technique in which an inclined surface (thrust relief) which extends from a circumferential end portion of the half thrust bearing by a length of an approximate half of the height of a top portion (outer diameter end at a circumferential center of the half thrust bearing) is formed on a sliding surface of the half thrust bearing, thereby reducing an inclined angle of the inclined surface relative to the sliding surface (see JP 2013-238277 A).